How to edit curve, but not ruined tilt settings?
I think you might want to change tilting to Z-Up under the Properties Window > Object Data Tab > Shape Panel 

Although it is not perfect it will probably be the closest to a correct "always up" tilt. You can then manually adjust whichever parts are not supposed to point up, which I believe are probably a minority compared to the tilting curves.

From my admittedly limited testing with Z-Up changing other parts of the curve has no effect on the already established tilts